Does Caffeine Cause Dehydration? No!

Darcy O'Neil :: December 31, 2009 3:17 PM

No! No! No! In normal amounts (up to 5 cups of coffee) the caffeine content does not cause dehydration and there is a lot of scientific research to back that claim up. However, if you perform an Internet search for the terms “caffeine dehydrate hangover” the top results come back saying that it does. Now I will say again “No it doesn’t!”. This is a major flaw in search engines algorithms because the older the page and the more people that link to it, the more authority it has, but it doesn’t mean it’s right. These search results only help to propagate out dated research and old-wives tales. So what’s the real story and what can be done?

This may seem like déjà vu to regular readers, but the caffeine dehydration myth is one of my pet peeves. So many people believe this myth that they stop drinking coffee when they have a hangover, suffering needlessly. Avoiding coffee during a hangover causes caffeine withdrawal, compounding the severity of the hangover.

Events, like New Years Eve, are full of stories on how to deal with a hangover, and most say to avoid caffeine, which is wrong. The reality is that caffeine will actually make your hangover more tolerable.

Caffeine does not have any diuretic effect at less than 550mg of caffeine (i.e. it won’t start dehydrating you until your fifth cup of coffee). So, when you have a hangover, it is absolutely OK to have a coffee. In fact, I seriously recommend it. Caffeine withdrawal is nasty, and causes headaches and lethargy. Caffeine is a perfect companion to a hangover, even more so if you are a regular coffee drinker.

Additional reading: Hangover Tips and My Love Affair with Caffeine

What Can We Do to Fix This Widely Held Belief?

1. If you have a blog, post an article and quote the research (given below)

2. Link to this article. In the 4+ years I’ve been writing Art of Drink I’ve never asked for link backs. Today I’m going to make an exception and ask that people link to this story. Why? Because search engines, Google specifically, ranks pages higher if they have many links pointing to the page. The reason being that if a lot of people link to a page, it must be important. Sadly, it just gives people the wrong answer, let’s give people the right answer.

3. If you link to this article, make sure the link contains the anchor text (words) “caffeine, dehydrate and hangover”. This helps Google figure out the topic. For example use the following link: Caffeine in coffee does not increase dehydration during hangovers.

If there are enough links, with proper anchor text, then whenever people search for this myth, the first thing they will see in the results is: “Does Caffeine Cause Dehydration? No!” which should be pretty clear.

4. If you are a bartender, spread the word.

5. Twitter, Facebook, Digg, Mixx, Stumble, or whatever other social network gadgetry you use, to promote the truth.

So a Happy New Year to all and to those that wake up with a nasty hangover, do enjoy a good cup of coffee and make your day a little better.

These are some of the applicable research papers, please feel free to cut and paste.


The effect of caffeinated, non-caffeinated, caloric and non-caloric beverages on hydration.
Grandjean AC, Reimers KJ, Bannick KE, Haven MC. The Center for Human Nutrition, Omaha
(Journal of the American College of Nutrition, October 2000)

Conclusion: This preliminary study found no significant differences in the effect of various combinations of beverages on hydration status of healthy adult males. Advising people to disregard caffeinated beverages as part of the daily fluid intake is not substantiated by the results of this study.

Urinary caffeine after coffee consumption and heat dehydration.
Chambaz A, Meirim I, Décombaz J. Nestlé Research Centre, Nestec Ltd, Lausanne, Switzerland.
(International journal of sport Medicine, July 2001)

Conclusion: These results suggest that the rise in circulating caffeine due to delayed metabolic clearance was partly opposed by a sizeable elimination in sweat. Therefore, heat dehydration did not lead to higher concentration of caffeine in urine after coffee ingestion.

Caffeine, body fluid-electrolyte balance, and exercise performance.
Armstrong LE. Departments of Kinesiology, Nutritional Sciences, and Physiology & Neurobiology, University of Connecticut (International journal of sport nutrition and exercise metabolism, June 2002)

Conclusion: The scientific literature suggests that athletes and recreational enthusiasts will not incur detrimental fluid-electrolyte imbalances if they consume coffee beverages in moderation and eat a typical U.S. diet. Sedentary members of the general public should be at less risk than athletes because their fluid losses via sweating are smaller.

Caffeine ingestion and fluid balance: a review.
Maughan RJ, Griffin J. School of Sport and Exercise Sciences, Loughborough University, Leicestershire, UK
(Journal of human nutrition and dietetics, December 2003)

Conclusion: The most ecologically valid of the published studies offers no support for the suggestion that consumption of caffeine-containing beverages as part of a normal lifestyle leads to fluid loss in excess of the volume ingested or is associated with poor hydration status. Therefore, there would appear to be no clear basis for refraining from caffeine containing drinks in situations where fluid balance might be compromised.

Rehydration with a caffeinated beverage during the nonexercise periods of 3 consecutive days of 2-a-day practices.
Fiala KA, Casa DJ, Roti MW. Department of Kinesiology in the Neag School of Education at the University of Connecticut (International journal of sport nutrition and exercise metabolism, August 2004)

Conclusion: In summary, there is little evidence to suggest that the use of beverages containing caffeine during nonexercise might hinder hydration status.

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